500 Mr. D. Sharp and Mr. F. Muir on the Comparative 
A less modified form is found in Xantholinus (Hulissus) 
chalybeus (Pl. LILI figs. 68, 68a) from Brazil ; in which the distal 
end of the median lobe is short and tubular, drawn out into a point 
on the ventral side, the median foramen being situate in the ventral 
chitinous sclerite at the base of the short tubular distal end, 
X. phoenicopterus is also less modified than X. glabratus, the 
lateral lobe being much larger and the median foramen on the 
ventral sclerite, 
Paederus riparius (Pl. LIIT figs. 69, 69a). 
The median lobe broad, slightly flattened and slightly bulbous 
at base, the dorsal distal margin projecting beyond the ventral, 
the median orifice being on ventral face beneath this projection ; the 
median foramen small, near base slightly dorsal. The lateral lobes 
broad, flattened, with curved pointed apices projecting beyond end 
of median lobe, closely applied to sides of it, and attached to it near 
the ventral edge of median foramen. Internal sac with large 
curved spine (a) at base. Apex of sac not examined. 
Lathrobiwm brunnipes. 
The median lobe bulbous and membranous, except on the ventral 
basal part which is chitinous ; median orifice at tip ; median foramen 
small, about the middle. Lateral lobes consolidated into a single 
body, broad at base and narrow at apex where there are two small 
points; a groove runs along the ventral side. They form the 
strongest part of the aedeagus and are consolidated to the ventral 
face of the median lobe from the edge of the median foramen to the 
tip. Internal sac not examined. 
L. fulvipenne is of the same type as L. brunnipes, but the left 
lateral lobe appears to be absent and the right is large and projects 
as a curved spine ; there is also a chitinous support on the dorsal 
side of the median orifice. 
L. boreale. 
The same type as L. brunnipes, the lateral lobes being consolidated 
into a single piece, the tip being pointed and turned down like a 
small hook, the median ventral line being keeled, not grooved. 
The dorsal margin of the median orifice is supported by a small 
chitin plate and a strong chitin piece with two hooks at the end 
projects from the basal part of the internal sac. On each side of 
the internal sac, near the base, is a patch of chitinous flat scales, 
prolonged into prongs on the basal edge. When the sac is evaginated 
the two-hooked piece on the dorsal side of the base turns over and 
